1. Field of the Invention
Vehicle roof rails are mounted onto a roof of a vehicle for the purpose of putting a load on the roof rails.
2. Description of the Related Art
Generally, in a conventional roof rail, a rail portion and leg portions to be mounted onto a roof of a vehicle are provided as separate parts. That is, after the rail portion and the leg portions are produced separately, they are assembled into a roof rail. The roof rail assembled thus is then mounted onto a roof of a vehicle. Further, in the conventional roof rail, the rail portion is constituted by a special-shape metal pipe and each of the leg portions attached to the rail portion is constituted by a metal mold casting or a synthetic resin as disclosed in JP-A-8-2336.
In the conventional roof rail, however, the drawback to the appearance thereof is that a joint is observed in the connection portion between the rail portion and each of the leg portions. Further, being made of a metal, the rail portion is heavy in weight, and has a disadvantage from the points of view of energy saving, improvement in fuel cost, etc. Further, since the rail portion and the leg portions are assembled into a roof rail after they are produced separately, not only special care is required for keeping the strength of the connection portion between the rail portion and each of the leg portions but also the process for production of the roof rail is apt to be complicated so that connection parts are required for connecting the leg portions to the rail portion. Accordingly, there is a heavy burden both on production and on production cost.
To make improvement against the problems in the aforementioned two-parts-type roof rail, a vehicle roof rail of a thermoplastic resin having a rail portion and leg portions integrally molded with the rail portion has already been proposed. Specific examples of the proposed roof rail are described in JP-A-9-109783, JP-A-9-183166, JP-A-9-142226, JP-A-9-175280, JP-A-10-35366, JP-A-9-30334, JP-A-10-15981, JP-A-10-193378, JP-A-10-151993, and the like.
In each of these proposals, there is proposed an integrally-molded vehicle roof rail of a thermoplastic resin reinforced with high-density glass fiber. There is, however, no description of the problem that both external appearance and external surface characteristic of the resulting roof rail might be spoiled remarkably because of appearing in relief of glass fiber, or the like, in the surface. Hence, it is impossible to find any description and any disclosure of an improvement against the problem.
For example, JP-A-9-109783 discloses that mount leg portions and a rail body portion are integrally molded from a glass-fiber-mixed synthetic resin and that a hollow portion is formed in the whole or a part of the rail portion by hollow injection molding. Although JP-A-9-109783 makes a proposal to produce a roof rail in which a joint between the rail portion and each of the mount leg portions is eliminated, there is no description concerning the external appearance of the outer surface of the roof rail.
Further, JP-A-9-183166 makes a proposal concerning the hollow structure of a vehicle roof rail of a synthetic resin having a hollow portion formed by hollow injection molding and concerning a method for forming the hollow. Further, JP-A-9-142226 and JP-A-9-175280 make proposals concerning a vehicle roof rail having a core material buried therein, concerning a method for molding the roof rail and concerning a vehicle roof rail having a member buried therein. In any one of those proposals, there is no description concerning the outer surface and external appearance of the roof rail.
Although JP-A-10-35366 and JP-A-9-30334 also disclose the structure of a vehicle roof rail, a method for producing the roof rail, etc., there is no description concerning the external appearance of the outer surface of the roof rail and a method for molding a roof rail having a good outer surface.
Further, JP-A-10-15981 makes a proposal to form a hollow by hollow injection molding to thereby make improvement against sinking, swelling, etc. caused by shrinking behavior at the time of molding. Further, JP-A-10-193378 makes a proposal to use a specific polyamide resin to thereby suppress an eccentric portion caused by hollow injection molding. In any of the proposals, there is no description concerning the problem of the external appearance of the outer surface caused by appearing in relief of glass fiber, or the like, in the surface.
Although JP-A-10-151993 further proposes the arrangement and the structure of a mold in a hollow injection molding method, there is also no description concerning the problem of the external appearance of the outer surface caused by appearing in relief of glass fiber, or the like, in the surface.
On the other hand, the aforementioned hollow injection molding method using means for forming a hollow portion has already been put into practice as a hollow injection molding method generally as disclosed in JP-A-57-14968. Further, an apparatus and a pressurized gas injection nozzle used in molding have already been disclosed in JP-A-5-177668 filed by the applicant of the present invention, or the like.
As will be understood, for example, from the disclosure of a roof rail of Nylon 66 containing 53% by weight of glass fiber in Embodiment 1 in JP-A-9-109783, a thermoplastic resin reinforced with a large loading weight of glass fiber, or the like, is used in the conventional vehicle roof rail of resin.
When such a reinforced thermoplastic resin filled with high-density glass fiber, or the like, is used, however, glass fiber, or the like, is apt to come to the surface, especially, the outer surface of the resulting roof rail to thereby spoil the surface characteristic of the roof rail. The roof rail having spoiled surface characteristic and spoiled external appearance characteristic after molding lacks its dignity as a whole. Accordingly, it is difficult to satisfy high-grade external appearance performance necessary for an exterior member of a vehicle before or after painting. In the case where the conventional vehicle roof rail is molded, particularly when it is molded by the hollow injection molding method, there is a risk of remarkable surface degradation in the external appearance of the roof rail.